- Title
- The role of the (pro)renin receptor in the pathogenesis of preeclampsia
- Creator
- Schofield, Lachlan
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2025
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- This thesis will describe the role of the (pro)renin receptor ((P)RR; ATP6AP2) in the hypertensive pregnancy pathology, preeclampsia. Preeclampsia is a systemic syndrome that occurs in 3 to 5% of pregnant women and classically manifests as new-onset hypertension with maternal organ dysfunction and/or placental dysfunction after 20 weeks of gestation. The (P)RR and its soluble form, s(P)RR, have become of recent interest in the context of preeclampsia. Both are involved in renin-angiotensin signalling (RAS) as not only can they activate prorenin and renin, thus influencing levels of angiotensin II (Ang II), but s(P)RR has now been shown to directly interact with and stimulate the angiotensin II type 1 receptor (AT1R; AGTR1). Levels of both placental (P)RR and maternal circulating s(P)RR are elevated in patients with preeclampsia, and higher levels of circulating s(P)RR are associated with increased systolic blood pressure in male mice. As such, my research focused on three key aims. Aim 1; highlight that the (P)RR is essential for placental development. Aim 2; show that the s(P)RR has an adverse effect on maternal endothelial dysfunction in pregnancy by assessing key clinical symptoms of preeclampsia (blood pressure, fetal growth, and vascular dysfunction). Aim 3; elucidate that endothelial dysfunction induced by the s(P)RR is occurring via the AT1R and can be blocked by the (P)RR antagonist PRO20. To determine the role of (P)RR within the placenta, we developed a placental-specific ATP6AP2 knockdown in a mouse model. Following this reduction, stereological analysis showed a decrease in trophoblast volume density in conjunction with a reduction in syncytiotrophoblast barrier thickness. Moreover, while fetal and placental weights remained unchanged, the fetal-placental weight ratio was significantly decreased in the placental ATP6AP2 knockdown mice. In a human first trimester extravillous trophoblasts cell line, we further demonstrated that knocking down ATP6AP2 expression using an siRNA impaired trophoblast proliferation, migration and invasion in vitro. Together, these studies demonstrated that (P)RR expression is necessary for appropriate trophoblast development and placental function. Pregnancies complicated by preeclampsia have elevated maternal s(P)RR levels, so we next sought to assess the effect of s(P)RR on maternal endothelial dysfunction by assessing key clinical symptoms of preeclampsia. Following treatment with s(P)RR, human uterine microvascular endothelial cells (HUtMECs) exhibited significant increases in markers of endothelial dysfunction at both the mRNA and protein level in vitro. Treatment with s(P)RR impaired endothelial tube formation, while also increasing endothelial adhesion with peripheral blood mononuclear cells. Together these outcomes demonstrated that elevated s(P)RR impairs endothelial function in vitro. Using an adenovirus to overexpress circulating s(P)RR in pregnant rats from day 8 of gestation, we then showed that pregnant rats with high circulating s(P)RR levels developed hypertension and exhibited renal vascular dysfunction. Fetal weights were also significantly decreased in pregnant rats overexpressing circulating s(P)RR. Collectively, these studies demonstrated that elevated s(P)RR produces a preeclampsia-like phenotype both in vitro and in vivo. Given that elevated s(P)RR was shown to induce maternal endothelial dysfunction, we next assessed the therapeutic potential of targeting the s(P)RR using the antagonist, PRO20. Using HUtMECs, s(P)RR-induced endothelial dysfunction was shown to be diminished at both the mRNA and protein level following PRO20 treatment, while neither Aliskerin (renin inhibitor) or Losartan (AT1R inhibitor) prevented s(P)RR-induced endothelial dysfunction. The actions of s(P)RR were inhibited however, when AGTR1 gene expression was ‘knocked down’ by pre-treating HUtMECs with an AGTR1 siRNA, supporting the hypothesis that the s(P)RR is causing endothelial dysfunction through its direct interaction with the AT1R. As such, we used in silico modelling to better understand the s(P)RR-AT1R interaction. Modelling highlighted that s(P)RR and Losartan interact with LYS199 on AT1R, with the s(P)RR-AT1R complex likely inducing conformational changes that obstruct Losartan binding. Moreover, PRO20 was predicted to interfere with s(P)RR-AT1R complex formation. Therefore, specifically targeting the s(P)RR could prove a novel therapeutic strategy to prevent overactivation of the AT1R in patients with preeclampsia. Overall, the work outlined in this thesis has greatly added to the body of information surrounding (P)RR and the s(P)RR in pregnancy and within the context of preeclampsia. In particular, it is the first to report the relationship between placental (P)RR expression and trophoblast development as a foundation of placental function. Moreover, we have shown that elevated circulating s(P)RR, in part, contributes to the maternal endothelial dysfunction seen in preeclamptic pregnancies, with this dysfunction likely being driven through the direct interaction between s(P)RR and AT1R. As such, therapeutic inhibition of s(P)RR to prevent its interactions with AT1R could prove to be an effective treatment for preeclampsia.
- Subject
- (pro)renin receptor; preeclampsia; renin-angiotensin signalling; placental (P)RR expression; trophoblast development
- Identifier
- http://hdl.handle.net/1959.13/1516398
- Identifier
- uon:56975
- Rights
- Copyright 2025 Lachlan Schofield
- Language
- eng
- Full Text
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